The present invention relates to a method for correction of a trapezoidal distortion of images in image processing for achieving improved medium-image registration. The present invention also relates to a method for controlling a printing device by performing a method for the correction of the trapezoidal distortion of images in image processing for achieving improved medium-image registration. The present invention further relates to a printing device comprising a controller for performing the methods according to the present invention.
Pressure differences in an image transfer or transfuse nip of a printing device can cause a medium to change direction. This change in direction introduces an undesirable image length difference of an image registered onto a medium by means of the printing device. In particular, the image length difference is present at opposite sides of the image. Although not quite correct, this type of image deformation is referred to as a trapezoidal distortion. A trapezoidal distortion leads to errors in medium-image registration. It is known to reduce this distortion by adjusting the pressure differences in the printing device with a mechanical setup. The known method to correct trapezoidal distortions has several drawbacks. A major drawback of the known method is that specific, relatively complicated, moveable mechanical parts have to be applied which makes the known method relatively expensive. Moreover, the moving mechanical parts applied are subjected to wear which is detrimental for the reliability of the known method to correct trapezoidal distortions.